Monoclonal antibodies against the 28KD protein of S. mansoni

ABSTRACT

A hybridoma is provided which provides a monoclonal antibody of isotope IgG2a, which recognizes a strip corresponding to a peptidic fragment of 8kD, isolated by controlled proteolysis of the 28kD polypeptide of S. mansoni.

This is a division of application Ser. No. 07/681,468, filed on Apr. 4,1991, now abandoned; which is a continuation of Ser. No. 07/492,358,filed on Mar. 9, 1990, now abandoned; which is a continuation of Ser.No. 07/069,989, filed on Jul. 6, 1987, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a peptide isolated from the 28 KDprotein of S. mansoni, which bears one or more epitopes and to itsprocess of isolation, as well as to monoclonal antibodies adapted torecognize the peptidic antigenic fractions thus isolated and totherapeutic compositions adapted to induce neutralizing anti-bodysynthesis, which compositions comprise said peptide alone or inassociation with other suitable substances.

BALLOUL et Al. (MOLECULAR AND BIOCHEMICAL PARASITOLOGY, 17 (1985) p.105-114) described the synthesis in vitro of an antigen constituted by apolypeptide having a molecular weight of 28 KD and an isoelectric pointcomprised between 6.3 and 6.8, which constitutes a translation productin vitro of total RNA of Schistosoma mansoni.

The above Authors have pursued their research with the object ofisolating from this polypeptide of 28 KD and of identifying, thepeptidic epitope or epitopes responsible for the antigenic properties.

It is known to analyze the peptides which constitute proteins isolatedfrom SDS gels, by partial digestion of said proteins by a protease in abuffer containing SDS; stable partial digestion products are obtained,which are composed of numerous peptides whose molecular weights aresufficiently high for it to be possible to separate them on 15% SDSacrylamide gels (CLEVELAND et Al., THE JOURNAL OF BIOLOGICAL CHEMISTRY,252, p. 1102-1106, (1977)).

Applicants have sought to isolate, from the 28 KD protein of S. mansoni,the one or more peptides bearing the anti-Schistosoma antigenic activityshown by the 28 KD protein, and have made use for this purpose oftechniques for isolating peptidic fragments by proteolysis described inthe prior art.

GENERAL DESCRIPTION OF THE INVENTION

It is an object of the present invention to provide a process forisolating a peptide bearing at least one epitope, by proteolysis,characterized in that the 28 KD protein of S. mansoni is subjected tothe action of V8 protease in Tris-HCl buffer pH 6.8 containing SDS, inthat the proteolysis reaction is stopped by the addition of a mixture of2-mercaptoethanol and SDS, then it is brought to boiling at 100° C. fora short time, to collect a peptide of which the antigenic activity ischecked by means of antibodies of a polyclonal serum or of monoclonalantibodies.

In a preferred embodiment of the process according to the presentinvention, the enzymatic digestion of the 28 KD protein by the V8protease is performed for 30 minutes at 30° C.

In another preferred embodiment of the process according to the presentinvention, the mixture used to stop the proteolysis reaction comprises2-mercaptoethanol in the proportion of 1 μl per 3 μl of 10% SDS.

In yet another preferred embodiment of the process according to thepresent invention, the Tris-HCl buffer in which the 28 KD protein isdissolved is a buffer 100 mM to 125 mM and contains 0.08 to 0.12% ofSDS.

In another preferred embodiment of the process according to theinvention, the checking of the antigenic activity of the peptideisolated by proteolysis, which is done by Western blotting by means of aanti-28 KD polyclonal serum of rat, rabbit or the like, reveals, bymeans of antibodies labelled with peroxidase, directed againstimmunoglobulins of rat, rabbit, mouse or the like, a 6 KD peptidicepitope.

In yet another preferred embodiment of the process according to theinvention, the checking of the antigenic activity of the peptideisolated by proteolysis, which is done by Western blotting by means ofan anti-28 KD monoclonal antibody reveals a peptidic epitope of 8 KD.

It is also an object of the present invention to provide a peptidicfragment, characterized in that it is isolated from the 28^(KD) proteinof S. mansoni by controlled proteolysis, in that it has a molecularweight of 6 KD and in that it is recognized by anti-28 KD polyclonalserum of rabbit, of rat or the like.

It is also an object of the present invention to provide a peptidicfragment, characterized in that it is isolated from the 28 KD protein ofS. mansoni by controlled proteolysis, in that it has a molecular weightof 8 KD and in that it is recognized by an anti-28 KD monoclonalantibody, of isotype IgG2a (W 2 AD 12).

Moreover the present invention has the object of providing a hybridomanamed M 5 BD 9, which provides IgM isotype monoclonal antibodies whichrecognize the 28 kD antigen.

It is also an object of the present invention to provide a hybridomanamed W 2 AD 12, deposited at the CNCM on 9 May 1986 under No. I-553,which provides mono-clonal antibodies of IgG2a isotype which recognize astrip corresponding to a peptidic fragment of 8 KD, isolated bycontrolled proteolysis of the 28 KD polypeptide of S. mansoni.

According to the present invention, the hybridomas M 5 BD 9 and W 2 AD12 are obtained by proceding as follows:

Monoclonal antibodies directed against the group of 28 kD proteins ofSchistosoma mansoni were obtained by rat x rat homologous cellhybridization using the myelomatous strain of rat LOU IR983F (Bazin etColl. 1980 Ann.Immunol. (Institut Pasteur) 131 D: 359), and spleencultures of LOU rat immunized with 50 μg of the 28 kD group of proteinsof S. mansoni, in the presence of complete Freund adjuvant, in twosubcutaneous injections of 25 μg, at 15-day intervals.

After fusion, the anti-28 kD antibody-producing cells were selected byradioimmunological tests on plates. A homogenate of adult worms is fixedto polyvinyl plates, then contacted with the antibodies present in thesupernatants of the hybrid cultures. The antigen-antibody linkage isthen revealed by the addition of a second antibody labelled with iodine¹²⁵ I, directed against rat IgGs. The positive cells in this test werecloned by the method of limiting dilution.

It is in addition an object of the present invention to provide avaccinating composition against S. mansoni which is characterized inthat it contains at least one peptide fragment of 28 kD of S. mansoniisolated by controlled proteolysis, associated with a suitable vehicle.

In an advantageous embodiment of the vaccinating composition accordingto the present invention, the latter contains at least one peptidefragment of 6 KD and/or of 8 KD associated with a suitable vehicle.

In another advantageous embodiment of the vaccinating compositionaccording to the present invention, the latter contains at least onepeptide fragment of 28 KD of S. mansoni isolated by controlledproteolysis, associated with the epitope of the 38 KD antigen, as wellas with a suitable vehicle.

The epitope of the antigen of MW 38 KD is an oligosaccharide which formsthe subject of French Patent Application No. 86 06281 of 30 Apr. 1986 inthe name of Applicants.

Besides the foregoing features, the invention comprises other features,which will emerge from the description which follows.

The invention will be better understood by means of an example ofperforming the process according to the present invention and examplesof characterization of the antigenic activity of the peptide accordingto the invention.

It must however be well understood that this example of its practice, isgiven purely by way of illustration of the invention, of which it doesnot constitute in any way a limitation thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates Western blotting, in which:

block 1 illustrates in its lower portion the peptide isolated byproteolysis, and in the upper portion the 28 kD protein,

block 2 represents the blot obtained with healthy rabbit serum,

block 3 represents the blot obtained with monoclonal antibodies comingfrom the hybridoma W2 AD 12; and

block 4 represents the blot obtained with polyclonal rabbit anti-28 kDserum.

FIG. 2 shows the results of Western blotting of the group of antigens of28 kD of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1 Preparation of thePeptide Isolated from the 28 KD Protein of S. mansoni

Step 1: Preparation of the antigen of 28 KD of S. mansoni

S. mansoni adult worms (Porto Rican strain) collected by perfusion ofthe portal vein in golden hamsters, were homogenized in a PBS buffer ina POTTER-ELVEHSEM homogenizer and the homogenisate was centrifuged at5000 rpm for 20 minutes.

About 2 mg of antigens were fractionated on 13% polyacrylamide gels inplates, by using the batchwise buffer system of Laemmli (described byLAEMMLI, NATURE (1970), 227, p. 680-685). After electrophoresis, thegels were dyed with COOMASSIE Brilliant Blue. The dyed strips were cutup with a scalpel and transferred into an elution gel constituted bycastings of support gel. Elution was performed at 40-60 V for 6 to 12hours. The speed of elution is a function of the percentage of the gelseparated and the molecular size of the proteins that are eluted.Migration of the samples was stopped at the interface of the layers of2M NaCl-glycerol.

When all the peptides had been eluted into the glycerol layer, theelectrophoresis was stopped and the samples were withdrawn by means of aPASTEUR pipette. The samples were then dialyzed against water to removethe SDS and the salts, before being concentrated by freeze-drying. Thefractionated proteins were then reanalyzed on 13% polyacrylamide gel, ina plate.

The protein of MW 28 KD obtained by the fractionation technique whichhas just been described, and which is characterized in that its inducesan antibody response and in that its antiserum immuno-precipitates thecorresponding 28 KD antigens among the in vitro translation productsboth of RNA of adult worms and RNA of Schistosomulas of S. mansoni, istaken for processing according to Step II below.

Step II: Isolation by proteolysis of a peptide of the protein 28 KD ofS. mansoni

10 μg of protein of 28 KD are dissolved in 30 μl of 125 mM Tris-HCLbuffer (pH 6.8) containing 0.1% of sodium dodecysulfate (SDS).

1 μg of protease V8 is added and the enzymatic digestion of the antigenof 28 KD is performed at 37° C. for 30 minutes, on the water bath.

The reaction is stopped by the addition of 1 μl of 2-mercaptoethanol and3 μl of 10% SDS. The whole is brought to 100° C. on the water bath for 6minutes.

Specimens constituted by a peptide of which the antigenic properties aredetermined, were collected

EXAMPLE 2 Analysis of the Antigenic Response of the Peptide of Example 1

10 μg of the peptide obtained in Example 1 were deposited on a 20%polyacrylamide gel. The peptide so-fractionated was transferred onto anitrocellulose sheet as described by TOWBIN et Al. (1984, J. Immunol.Methods 72, p. 471).

The nitrocellulose sheet was first saturated with a 3% BSA solutionbuffered by mono- and disodium phosphate 10 mM pH 7.2 containing 0.15MNaCl-50 μl of antibodies, which antibodies were either antibodies of apolyclonal serum of rat or of rabbit or monoclonal ascites antibodies,or antibodies obtained from a hybridoma, specifically from hybridoma W 2AD 12, M 5 BD 9.

Antigen and antibody are left in contact overnight at room temperature,to obtain a "Western blot" which is washed three times for thirtyminutes in phosphate buffer.

Antibodies labelled with peroxidase (supplied by PASTEUR PRODUCTION)directed either against rabbit immunoglobulins (in the case ofpolyclonal antibodies), or against rat immunoglobulins (in the case ofmono-clonal antibodies), were then added and incubated with the "blot"for 2 hours. Three further washings were carried out and the presence ofimmunocomplexes was revealed by the addition of a solution containing20% of cold methanol, 30 mg of 4-chloro-1-naphthol, 0.1% of H₂ O₂ per100 ml of phosphate buffer, 0.15M NaCl.

The Western blotting is shown in FIG. 1 attached in which:

block 1 shows in its lower portion the peptide isolated by proteolysis,according to the invention and at its upper portion the protein 28 KD;

block 2 represents the "blot" obtained with a healthy rabbit serum;

block 3 represents the "blot" obtained with mono-clonal antibodiescoming from the hybridoma W 2 AD 12;

block 4 represents the "blot" obtained with poly-clonal rabbit anti-28KD serum.

This Western blotting shows that the monoclonal antibody W 2 AD 12bearing a cytotoxic activity with respect to the post-infecting larvaeof Schistosoma mansoni recognized a fragment of 8 kD derived from theprotein of 28 kD.

The recognition by an antibody of anaphylactic class suggests theimportance of this peptide in the induction of a protective responsewith respect to S. mansoni.

The epitope borne by a fragment of 6 kD recognized by the rabbit serumis not recognized by the rat mono-clonal antibody suggesting that therecognition of this or that epitope of the 28 kDa antigen is specific asto species.

EXAMPLE 3 Checking of the Recognition of the Antigenic Peptide Accordingto the Present Invention with Monoclonal Antibodies

A. Search for a peptidic epitope of restricted size among theproteolysis products of the 28 KD antigen, enabled a fragment of 8 KD tobe revealed recognized specifically by the monoclonal antibody ofisotype IgG2a, obtained from the hybridoma W 2 AD 12.

The cytotoxic activity (illustrated in Table 1 below) of this monoclonalantibody in vitro tests involving eosinophils, suggests the importanceof the one or more epitopes borne by this peptide of 8 KD.

                  TABLE 1                                                         ______________________________________                                        Eosinophil-dependent Cytotoxicity                                             Source of antibodies .sup.a                                                                   Percentage of cytotoxicity ± S.D. .sup.b                   ______________________________________                                        Serum of rat carrying the                                                                     66.9 ± 26.0                                                hybrid subcutaneous tumor                                                     W 2 AD 12                                                                     Serum of rat carrying the                                                                      7.3 ± 1.06                                                subcutaneous tumor of                                                         IR983F cells                                                                  Serum of rat immunized by                                                                     69.9 ± 22.9                                                protein 28 kD                                                                 Serum of rat infected for                                                                     74.3 ± 23.5                                                4 weeks with S. mansoni                                                       Serum of healthy rat                                                                          5.0 ± 4.2                                                  ______________________________________                                    

The cytotoxicity tests were carried out according to the conditionsdescribed by Capron et Coll. (Eur. J. Immunol., 8, 127-133, 1978).

a) The schistosomulas were presensitized during 18 hours, in thepresence of 100 μl of different serums (final dilution 1/16) heated 1hour at 56° C.,

b) Percentage cytotoxicity (mean ±standard deviation from the mean) wasmeasured after 48 hours of incubation of the schistosomulas sensitizedin the presence of peritoneal cells from healthy rats (ratio effectivecells/target=6000/1).

The anti-28 KD rabbit serum did not recognize the one or more epitopesborne by this peptide, but recognized another peptide, of 6 KD.

The monoclonal antibody of W 2 AD 12 recognized the two peptides of thegroup of antigens of 28 KD.

B. The monoclonal antibody of IgM, isotype obtained from the hybridoma M5 BD 9 only recognized one of the two proteins of the 28 kD group.

FIG. 2 attached shows the results of Western blotting of the group ofantigens of 28 kD according to the invention with monoclonal antibodiesof M 5 BD 9, W 2 AD 12 and with polyclonal rabbit serum, such asdescribed above.

We claim:
 1. Hybridoma, W2AD12, deposited at the CNCM on May 9, 1986 asNo. I-553 which provides a monoclonal antibody of isotype IgG2a, whichrecognizes a strip corresponding to a peptidic fragment of 8 KD,isolated by controlled proteolysis of the 28 KD polypeptide of S.mansoni.
 2. A monoclonal antibody produced by the hybridoma of claim 1.3. The monoclonal antibody of claim 2, wherein said controlledproteolysis comprises subjecting the 28 KD polypeptide of S. mansoni tothe action of the protease V8 in Tris-HCl buffer by adding a mixture of2-mercaptoethanol and SDS, then boiling the same at 100° C. for a shorttime, to collect a peptide whose antigenic activity is determined bymeans of a polyclonal serum or by monoclonal antibodies.
 4. Themonoclonal antibody of claim 2, wherein the enzymatic digestion of the28 KD protein by the V8 protease is performed for 30 minutes at 30° C.5. A method of selecting peptidic epitopes carried by a 28 KDpolypeptide antigen of S. Mansoni, which comprises contacting saidpeptidic epitopes with the monoclonal antibody produced by the hybridomaof claim
 1. 6. The method of claim 5, which further comprises labellingsaid monoclonal antibody prior to contacting said peptide epitopes withthe same.
 7. The method of claim 5, which further comprises detectingsaid labelled monoclonal antibody after contacting said peptidicepitopes with the same.